[issue15528] Better support for finalization with weakrefs
Richard Oudkerk
report at bugs.python.org
Sat Aug 4 21:24:31 CEST 2012
Richard Oudkerk added the comment:
> I don't quite understand the purpose of your suggestions. What can you do
> with it help, what you can not do with contextlib.ExitStack, atexit,
> __del__ method, weakref.WeakKeyDictionary or weakref.ref? I read the
> documentation, but the meaning eludes me.
finalize does not "compete" with contextlib.ExitStack, atexit and
weakref.WeakKeyDictionary. It only competes with __del__ and weakref
callbacks.
Points 1 and 2 in my first message are the main points. Also, read the
warning at
http://docs.python.org/py3k/reference/datamodel.html#object.__del__
which also applies to weakref callbacks.
Other problems with __del__:
* Ref cycles which contain an object with a __del__ method are immortal
* __del__ methods can "ressurect" the object.
There was actually a proposal to remove or replace __del__ methods in
Python 3000. See the "Removing __del__" thread(s):
http://mail.python.org/pipermail/python-3000/2006-September/thread.html#3797
As for weakref callbacks, I think they are just too difficult to use correctly
unless you are very familiar with them.
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